1. Field of the Invention
The present invention relates to a nitride semiconductor laser element that is less prone to uneven current injection near a cavity end face and that is thus less prone to a resulting abnormality in the current-optical output characteristic.
2. Description of Related Art
In a nitride semiconductor laser element having a ridge stripe-shaped waveguide, when an electrode is formed above a nitride semiconductor layered portion, it is commonly formed with the following layers interposed in between: a waveguide formed on the top surface of the nitride semiconductor layered portion, which is formed on a substrate; and an insulating protection film having an opening above the waveguide. As an example of a nitride semiconductor laser element so structured, the one proposed in JP-A-H11-330610 is shown in FIG. 20.
FIG. 20 is a cross-sectional view of the nitride semiconductor laser element 100 cut in the direction perpendicular to a ridge stripe-shaped waveguide region 115, that is, in the direction parallel to cavity end faces. The nitride semiconductor laser element 100 has, on a nitride semiconductor substrate 106 exhibiting n-type conductivity, the following layers laid one after another: an n-type crack prevention layer 107; an n-type clad layer 108; a light guide layer 109; an active layer 110; a p-type cap layer 111; a light guide layer 112; a p-type clad layer 113; and a p-type contact layer 114. Part of these layers and of the nitride semiconductor substrate 106 is then etched away to form the waveguide region 115 in the shape of an elevated stripe. Over the top surface of the nitride semiconductor substrate 106 and over the side surfaces of the waveguide region 115, there is formed, as an insulating protection film, a first protection film 104 having an opening above the waveguide region 115. The waveguide region 115 and a region nearby are coated with a p-type electrode 101. Over the part of the top surface of the nitride semiconductor substrate 106 other than where the p-type electrode 101 is located, there is formed a second protection film 105. On the p-type electrode 101 and the second protection film 105, a pad electrode 102 is formed. On the bottom surface of the nitride semiconductor substrate 106, an n-type electrode 103 is formed.
In this conventional nitride semiconductor laser element 100, the nitride semiconductor substrate 106 along with the different layers formed thereon is cleaved to produce cavity end faces. When this is done, there is a risk of the p-type electrode 101 exfoliating from the p-type contact layer 114 at a cavity end face. Where the p-type electrode 101 has exfoliated, no current is injected from the p-type electrode 101 into the different layers formed on the nitride semiconductor substrate 106. Thus, uneven current injection occurs, possible leading to a defect in the current-optical output characteristic.